Die casting machine



Sept- 6, 1966 R. w. PARKER 33270377 DIE CASTING MACHINE Filed March 30, 1964 INVENTOR.

United States Patent O 3,270,377 DIE CASTING MACHINE Robert W. Parker, Erie, Pa., assignor to Parker White Metal Company, Fairvew, Pa., a corporation of Pennsylvania Filed Mar. 30, 1964, Ser. No. 355,655 7 Clams. (Cl. 22-68) In die casting machines, difficulty has been experienced in getting good castings in all cavities of a multiple cavity mold. Metal tends to fiow into some of the cavities before the full die casting pressure is developed and the chilling of the initial flow of metal blocks complete filling of the mold cavity when the die casting pressure is subsequently developed.

This invention is intended to control the flow of molten metal to the individual cavities so that the cavities are filled in sequence with full die casting pressure applied as each cavity is filled. In a preferred form, a plunger moves along the sprue at a controlled rate, uncovering in sequence the runners to the individual mold cavities so that the filling of each mold cavity takes place under full die casting pressure.

In the drawing, FIG. l is a fragmentary section of a die casting machine, FIG. 2 is a section on line 2 2 of FIG. l, FIG. 3 is 'a section on line 3-3 of FIG. 2, and FIG. 4 is a fragmentary view of a modification.

The invention is shown applied to a cold chamber die casting machine although it is applicable to other types of die casting machines. The machine has a pour opening 1 through which the cold chamber 2 is filled with molten metal to 'a suitable level such as indicated by dotted line 3. After filling, -the shot plunger 4 is moved to the right and forces the semi liquid metal into a sprue 5 between the stationary mold 6 and a movable mold 7. Branching from the sprue 5 at suitably spaced points along the length of the sprue are runners Sa through 8]' inclusive respectively leading to mold cavities 9a through 9]' inclusive. The cavities are shown in the movable part 7 of the mold.

In the prior art machines, as the shot plunger 4 advanced, the metal would flow rapidly to the end of the sprue 5 with little pressure on the metal as it fiowed past the runners 8a, 8b, Sc, etc. Upon reaching the end of the sprue, full die casting pressure would develop and the flow into the mold cavity 9j most remote from the plunger would be under full die casting pressure from the start of the filling. Because it was filled under the full die casting pressure, the casting from cavity 9]' would be a sound casting. Sound castings would also be produced from some of the earlier cavities such as 9i, 9h, 9g, 9.

However, because the metal flowing past the earlier mold cavities such as 9a through 9d inclusive was not under full die casting pressure until 'after the sprue 5 had been filled, some metal could flow into the earlier mold cavities and chill before the full die casting pressure was developed. After the cavities 9 through 9]' had been completely filled, full die casting pressure would be available for the earlier mold cavities but the chilled metal would restrict or block the flow with the result that the earlier cavities 9a, 9b, 9c, etc. would not be completely filled and would not be sound castings.

The difficulty of incomplete filling of the earlier mold cavities is prevented by a plunger 10 having a sliding fit in the sprue 5. The upper end of the plunger 10 is connected by a pivot joint 11 to a cross head 12 guided on rods 13, 14. The pivot joint allows the plunger to swing with the movable mold 7 as the mold is opened if the plunger should momentarily stick to the casting. The cross head is connected to a piston rod 15 actuated by a piston 16 in a cylinder 17 filled with a suitable hydraulic fluid. The function of the plunger 10 is to 3,270,377 Patented Sept. 6, 1966 JCC oppose or ret-ard the fiow of die casting metal along the sprue 5 so that each of the mold cavities is completely filled under die casting pressure before the filling of the next cavity starts. The pressure exerted on the plunger 10 by the piston rod 15 i-s always less than the pressure exerted by the molten metal so the plunger 10 moves upward as the shot plunger 4 advances. The plunger 10, during its upward movement, first uncovers the runner 8a -and permits the filling of the mold cavity 9a. Because of the blocking action of plunger 10, adequate die casting pressure is available for filling the cavity 9a and the cavity is completely filled. The pressure on the molten metal developed by continued advance of the shot plunger 4 forces the plunger 10 still further upward uncovering successively the runners 8b, 8a, etc. and permitting sequenti-al filling of the mold cavities 9b, 90, etc., each under die casting pressure. In' each case, the filling of the preceding mold cavity preferably takes place and is com pleted before filling of the next mold cavity starts. Because of the blocking action of the plunger 10, it is not necessary that each cavity be completely filled before filling of a succeeding cavity is started; some overlap can be tolerated.

Two expedients are illustrated in FIG. 1 for controlling the upward movement of the plunger 10. In accordance with one expedient, a line 18 connected to a source of fluid pressure is `controled by a valve 19 leading to the upper part of the cylinder 17. The fluid pressure in the line 18 is sufficiently lower than the die casting pressure so that the pressure of the molten metal 'acting on the lower end of the plunger 10 forces the plunger to move upward and successively uncover the runners 8a, 8b, 8c as the shot plunger 4 advances. In accordance with the other expedient, a line 20 connects the top and bottom of the cylinder 17 through a restricted valve 21. The `restriction 21 causes a fluid pressure on the upper side of the piston 16 which opposes or retards the upward movement of the plunger 10 and thereby compels sequential filling of the mold cavities 9a, 9b, 9c, etc.

Another construction for controlling the plunger 10 is shown in FIG. 4 where a compressed air line 22 is connected through a valve 23 to the upper part of a tank 24 partly filled with oil 25. The lower part of the tank 24 is connected through a v-alve 26 and line 27 to the upper part of the cylinder 17. The lower part of cylinder 17 is connected to a vent line 28 open to atmosphere. When valve 23 is open, the air pressure forces oil into the upper part of cylinder 17 and forces piston 16 down to return the plunger 10 to the lowermost position. Valve 26 controls the flow of oil `to limit the rate of fiow of oil and thereby limit the 4rate of upward movement of the plunger 10 under die casting pressure.

In addition to obtaining better fill of the mold cavities, the air in the cold Chamber above the dotted line 3 which Would normally be vented through the mold -cavities is forced out through vents around the plunger 10 before the metal can move the plunger upward. This air accordingly does not flow through the cavities ahead of the metal. Also, because the plunger 10 is in the sprue 5, there is no air in the sprue to be forced into the mold cavities ahead of the metal. The elmination of air is an additional advantage.

By any construction, the mold cavities 'are filled in sequence under full die casting pressure and the metal has no chance to partially fill a mold cavity under little or no pressure and set up or chill in the cavity before the full die casting pressure is available.

From one aspect, the plunger 10 acts as a valve to successively open the runners leading to the individual mold cavities. From another aspect, the plunger 10 provides a vback pressure retarding the flow of metal along the sprue so the metal flowing from the sprue into the individual cavities is under pressure.

What is claimed as new is:

1. In a die casting machine, a stationary die, a movable die closed against the stationary die, a sprue between the dies, a plurality of runners spaced along the length of the sprue 'and respectively branching from the sprue into separate cavities, a chamber in lthe stationary die communicating with one end of the sprue, means for forcing molten metal under pressure from the chamber into said one end of the sprue, a plunger slidable in the sprue and presented toward s-aid one end of the sprue and initially blocking the fiow of metal into the runners, and means for controlling the movement of the plunger along the sprue to sequentially unblock the runners and permit sequential filling of the cavities under pressure.

2. In a die casting machine, a die having a plurality of cavities, a sprue having a plurality of runners spaced along its length -and each feeding a different mold cavity, means for forcing molten metal under pressure into one end of the sprue, a plunger slidable in the sprue and presented toward said one end of the sprue and initially blocking the fiow of metal into the runners, and means controlling the movement of the plunger along t-he sprue to sequentially unblock the runners and permit sequential filling of the cavities underpressure.

3. In a die casting machine, a die having a plurality of cavities, a sprue having a plurality of runners spaced along its length and each feeding a different mold cavity, means for forcing molten metal under pressure into one end of the sprue, a plunger slidable in the sprue and presented toward said one end of the sprue and initially blocking the fiow of metal into the runners, and means for retarding the movement of the plunger along the sprue under the pressure of the molten metal yto unblock successive runners and compel sequential filling of the cavities associated with the unblocked runners.

4. In a die casting machine, a stationary die, a movable die closed against the stationary die, a sprue between the dies, a plurality of cavities respectively fed from different Sections of the sprue spaced along its length, a chamber in the stationary die communicating With one end of the sprue, means for forcing molten metal under pressure from the chamber into one end of the sprue, and means for producing a back pressure retarding movement of the metal along the sprue to compel sequential filling of the cavities under pressure.

5. In a die casting machine, a stationary die, a movable die closed 'against the stationary die, a sprue between the dies, a plurality of cavities respectively fed from different Sections of the sprue spaced along its length, a chamber in the stationary die communicating with one end of the sprue, means for forcing molten metal under pressure from the chamber into one end of the sprue, a plunger slidable in the sprue and presented toward said one end of the sprue and initially blocking the fiow of metal from the sprue into the cavities, and means for controlling the movement of the plunger along the sprue to sequentially unblock the fiow of metal into the cavities and permit sequential filling of the cavities under pressure.

6. In a die casting machine, a stationary die, a movable die closed against the stationary die, a sprue between the dies, a plurality of cavities respectively fed from different Sections of the sprue spaced along its length, a chamber in the stationary die communicating With one end of the sprue, means for forcing molten metal under pressure from the chamber into one end of the sprue, a plunger slidable in the sprue and presented toward said one end of the sprue and initially blocking the fiow of metal from the sprue into the cavities, and means for retarding the movement of the plunger along the sprue to sequentially unblock the fiow of metal into the cavities and permit sequential filling of the cavities under pressure.

7. The machine of claim 4 in which the retarding means is a plunger in the sprue subject to a pressure less than the pressure of the molten metal.

References Cited by the Examiner UNITED STATES PATENTS 1,697,741 1/1929 Vaughan 22-68 2,447,355 8/1948 Morin 18 42 X 2,54l,592 2/1951 Lietaert 22 68 X 2,570,433 10/1951 Dodge.

2,672,653 3/1964 Sirnkins et al 18-30 X J. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examne'r. 

4. IN A DIE CASTING MACHINE, A STATIONARY DIE, A MOVABLE DIE CLOSED AGAINST THE STATIONARY DIE, A SPRUE BETWEEN THE DIES, A PLURALITY OF CAVITIES RESPECTIVELY FED FROM DIFFERENT SECTIONS OF THE SPRUE SPACED ALONG ITS LENGTH, A CHAMBER IN THE STATIONARY DIE COMMUNICATING WITH ONE END OF THE SPRUE, MEANS FOR FORCING MOLTEN METAL UNDER PRESSURE FROM THE CHAMBER INTO ONE END OF THE SPRUE, AND MEANS FOR PRODUCING A BACK PRESSURE RETARDING MOVEMENT OF THE METAL ALONG THE SPRUE TO COMPEL SEQUENTIAL FILLING OF THE CAVITIES UNDER PRESSURE. 